For a flat display panel such as a liquid crystal display (LCD) panel or an organic light-emitting diode (OLED) display panel, a thin film transistor (TFT) on an array substrate may serve as a switching TFT or a driving TFT.
In the flat display panel, there are different requirements on the characteristics of the switching TFT and the driving TFT. To be specific, it is required for the switching TFT to have a large on-state current so as to ensure its high switching performance, and it is required for the driving TFT to have a small on-state current so as to ensure its low-current driving performance.
Currently, an active layer of the TFT is usually made of poly-Si formed by subjecting a-Si to excimer laser annealing treatment, and mobility of carriers in the poly-Si is greater than that in a-Si. The mobility of the carriers in the poly-Si depends on a grain size, and the on-state current of the TFT depends on the mobility of the carriers. In other words, the larger the grain size of the poly-Si, the greater the mobility of the carriers and the larger the on-state current of the TFT. Hence, when manufacturing the switching TFT and the driving TFT on an identical array substrate simultaneously, it is required to control the grain sizes of the poly-Si for the switching TFT and the driving TFT, respectively, so as to meet different requirements of the switching TFT and the driving TFT on the on-state currents. However, with respect to TFTs of different types on the same array substrate, it is impossible for an existing excimer laser annealing process to form poly-Si with different grain sizes through crystallization in different degrees.
Hence, there exists such an urgent need to achieve the crystallization in different degrees through the excimer laser annealing process with respect to TFTs of different types on the same array substrate.